Today, bearing units are commonly used in automotive, aeronautics and other technical fields. These units provide high quality signals and transmissions, while allow integration in simpler and more compact apparatus.
Such a bearing unit generally comprises a bearing, and an impulse ring. Detection means are arranged in respect with the bearing unit so as to face the impulse ring. The impulse ring may comprise a target holder and a target. The target is preferably a magnetized portion including alternating north and south poles, whose number depends on bearing size, accuracy and particular application. With a bearing having suitable dimensions, impulse ring may be fixed to a rotating ring of this bearing, while detection means may be fixed to a non-rotating ring of this bearing or a stationary support or housing.
With a bearing having small dimensions, it may be necessary to position the detection means beside the bearing, while impulse ring is fixed to inner ring and extends radially beyond outer ring of the bearing. Together, bearing and impulse ring forms a bearing unit which can be fixed to a rotating shaft. However, when shaft, inner ring and impulse ring are rotating at high speed, target holder may be deformed.
It is known from FR-A-2 884 367 to provide a target holder with an inner tubular portion fixed to the rotating inner ring, an outer tubular portion that holds the target radially beyond the non-rotating outer ring, and a radial portion extending between the inner and outer portions. The radial portion has a specific shape and reinforcement ribs to avoid interference with the outer ring and to prevent deformation of the radial portion. However, the inner tubular portion and the radial portion form a right angle which can be damaged at high rotation speeds and vibrations. More precisely, the radial portion oscillates in respect with the inner tubular portion. The deformation between the tubular inner portion and the radial portion can be permanent. It can further induces material fatigue and then increases the risks of breaking. The target may be in an undesired position, temporarily or permanently, leading to a decrease of the measurement accuracy of the detection means.